The death toll from a capsized duck boat that sank Thursday night during a thunderstorm on a Missouri lake has jumped to 17, according to officials.

Five children were among those killed, according to a list of the victims released by the sheriff’s office Friday night. Nine of the 17 victims were reportedly related, and a list of names of those who died appears to confirm that.

Stone County Sheriff Doug Rader announced Friday morning that the number of fatalities had risen to 17 after the bodies of four people who had been missing were recovered. Seven people were being treated at a hospital, one with severe injuries that were not considered life-threatening, the sheriff's office added.

National Transportation Safety Board member Earl Weener said Friday that the dead included 16 passengers and one crew member. In all, there were 29 passengers and two crew members on board, he said.

Severe thunderstorms generating winds of up to 60 mph moved through the area when the Ride the Ducks boat encountered trouble around 7 p.m. local time (8 p.m. ET), reported NBC affiliate KYTV of Springfield.

Rader cautioned it was early in the investigation to draw any conclusions, but said he believed weather may have been the cause, as the tourist boat was buffeted by powerful winds on Table Rock Lake near Branson.

In a press conference Friday morning, Rader said he believed that there had been life jackets on the boat, but said he did not know if passengers were wearing them.

He also said there had been a captain and a driver on the boat. The captain survived, Rader said, but the driver did not.

Missouri Gov. Mike Parson visited with survivors and victims’ relatives on Friday. He said in a statement that of the 14 survivors, seven were injured, one seriously.

"What happened here last night was a heart-breaking tragedy, and we must all work together to support the victims and their families," Parson said in a statement.

Jim Patterson, president of Ripley Entertainment, which owns the duck boat tours in Branson, told "CBS This Morning" that the company was in the process of gathering more information about what led to the tragedy.

“It was a fast-moving storm that came out of basically nowhere is sort of the verbal analysis I’ve got,” Patterson told CBS.

But, he acknowledged, the boat “shouldn’t have been in the water if what happened, happened.”

According to NBC News' Al Roker, storms had been forecast for the area.

“There was one line [of storms] that already moved through earlier in the afternoon, and then that second line starts coming in around 5, 6 o’clock and by 7, right on top of Branson,” Roker said. “Moved through quickly, but boy, the damage was done.”

The incident was witnessed by horrified onlookers who described waves of up to 6 feet high.

Jennie Carr, who posted video on Facebook of the duck boat as it struggled in the surge, said she saw the vessel sinking into the waves, unable to move faster.

She told "Today" that she was on a larger showboat, whose captain told the crew to prepare life vests for people as the duck boat sunk. Some of the crew jumped into the water to try and help rescue riders.

"I went to the window, and I prayed and I cried," said Carr, who had never seen such towering waves on the lake. "There was nothing you could do," she added.

"It was sad to know that some of those people weren't going to get to go home," Carr said.

Carr's husband, Jeff, who was also on the showboat, said: "The waves were 6 feet tall. For a lake, that's pretty big."

Weener said Friday that good Samaritans helped rescue a number of people who were in the water after the accident. Some employees of the showboat "jumped in the water to save some of the victims," he said.

In a statement Thursday, Suzanne Smagala-Potts of Ride the Ducks Branson, said the company was saddened by the tragedy.

"This incident has deeply affected all of us," Smagala-Potts said. "We will continue to do all we can to assist the families who were involved and the authorities as they continue with the search and rescue."

She added, "The safety of our guests and employees is our No. 1 priority."

NEW VIDEO: This is video from the second duck boat that was also out on the water sent to us by Paul. He and family are visiting from Texas.

President Donald Trump sent his condolences in a tweet Friday morning.

“My deepest sympathies to the families and friends of those involved in the terrible boat accident which just took place in Missouri. Such a tragedy, such a great loss. May God be with you all!" he wrote.

The Coast Guard said there will be an attempt to raise the sunken vessel as part of the investigation.